This is true, but also really funny considering that even today the average windows sysadmin can still barely use powershell and relies on console clicking and batch scripts. A good unix admin can easily admin 10-100x the machines as a windows admin, and this was more true back in the early 00s. So the marketing on getting the facts was absolutely false.
Citation needed on that one. I've only worked with a minority of Windows sysadmins who are as incompetent as you say. And yeah, of course a good unix admin can run circles around a bad windows one, but the converse is just as true. A good Windows admin can run circles around a bad unix one. It has nothing to do with the operating systems and everything to do with technical competence of the individual.
There are a LOT more bad windows admins than bad unix admins though. The floor of being a unix admin is so much higher that it already filters out a lot of people. There are so many MSPs and small businesses with a windows admin that does everything through a console its crazy. You are right its all about the admin, but on average, the average linux admin is far more comfortable scripting than the windows admin.